Community Over Code EU (formerly known as ApacheCon EU) is happening next summer, and their Call for Papers is open until Jan 12, 2024!
Submissions on any topic related to the Apache Software Foundation, Apache projects, or the communities around those projects are welcome, and there are a list of specifically sought topics which include Big Data, Cassandra, Data Engineering, Search, and of course, Community. 
(See track descriptions.)
For more information, check out Community Over Code EU 2024: Call for Speakers @ Sessionize.com